


The Big Bad Tickle Monster

by TheSerpentGamer



Category: Undertale (Video Game)
Genre: Fluff, Other, Tickle fic, Tickling, tickle monster - Freeform, ticklish!asriel
Language: English
Status: Completed
Published: 2018-10-07
Updated: 2018-10-07
Packaged: 2019-07-27 11:33:38
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 4,331
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16218164
Author URL: https://archiveofourown.org/users/TheSerpentGamer/pseuds/TheSerpentGamer
Summary: THIS IS THE FIRST FIC I EVER WROTE AND POSTED, originally posted April 27th 2016Summary: Frisk and Asriel telling scary stories in their room. [WARNING: THIS IS A TICKLE FIC]





	1. Chapter 1

"Frisk? Wanna play upstairs?“ Asriel asked from across the table. 

Frisk nodded, picking up their plate to clean off the left overs from the dinner Toriel had made.

"Alright! I’ll meet you in our room.” Asriel called, jogging out of the kitchen and up the stairs to their shared bedroom. 

It had been about 6 months since monsters returned to the surface. After finding an empty place to settle near town, Frisk found a home with Toriel, Sans, Papyrus, Undyne, Alphys, and Flowey. A two-story house gave a generous amount of room for the family to live in while on the surface, and the basement gave Alphys a make-shift lab to work on helping Asriel to gain his form back. It was only a month ago that they were able to successfully take some of Frisk’s determination, Frisk’s soul, and give it to Flowey in order to restore Asriel’s being. After introducing the boy to his new surroundings and to those around him, he was quickly accepted with open arms into the family. Now, Frisk  
and Asriel share a room and live as the children that they are with their mom, Toriel.

After cleaning off the dishes and table, Frisk walked up the staircase and down the hall to the bright blue door with various drawings taped on it and a large sign with the words “FRISK AND ASRIEL’S ROOM” at the top. Frisk pushed open the door and saw Asriel laid on the small couch, head propped up while staring absent-mindedly out the window to the side. At the sound of the door opening Asriel’s head turned to look happily at Frisk, eyes wide and gleaming as if they were meeting for the first time in ages. 

“Howdy, Frisk! Whatcha wanna do?” Asriel asked, sitting up excitedly now that their best friend had returned. Ever since he returned from his soulless state, he had a lot of catching up to do. Frisk had to explain everything that had happened since he had left. They had been his guide through accepting his own absence and his new life. He always felt safe with the human around. When Asriel first met Frisk in his true form, when he shattered the barrier, they showed him incredible kindness and charity, forgiving him for all the awful things he had done. And when he returned again to the surface, he was immediately greeted by the human once more, who had given a fraction of their soul for him. Asriel never understood how Frisk would give up part of their own soul for a monster they barely knew, but Frisk was adamant that Asriel deserved it and there was no doubt they made the right choice. That seemingly unending kindness practically radiated off of Frisk with their every action. Asriel adored their loving nature that he felt every time he was near them. Though Frisk only had a fraction of a soul, their compassion, empathy and determination was just as strong as before. And now Asriel shared that love and kindness. He couldn’t be happier.

“I don’t know.” Frisk replied. They gazed out the window and saw the sun setting over the horizon. “Maybe we could… Tell scary stories!” 

“Okay! But not too scary, right?” 

Frisk giggled, walking over to their bedside table. “Okay. Not too scary.” Frisk dug around for a few seconds before pulling out a flashlight. “Okay let’s get under the covers on my bed!”

Asriel laughed excitedly and jumped onto the bed. Frisk’s bed was decorated with a purple, heart-covered comforter that he pulled over their heads sitting with his legs crossed and waiting for Frisk to begin. He watched as Frisk flicked on the flashlight, illuminating the space under the blanket, and tapped their chin thoughtfully. After a few moments of thinking and “hmm”-ing, Frisk’s face suddenly broke out with a more mischievous expression. Frisk leaned over the flashlight, gracing them with an eerie presence. 

“Alright. Here goes. This happened to me once, and I’ll never forget it. So, I was alone in my bedroom, it was really late and I was tired. I was just about to fall asleep when I heard something. A voice. The deep, raspy voice whispered my name. ‘Friiiiisk..’ I was shaking when I spoke very quietly: 'W-who’s there?’. It only chuckled in response. So I said a bit louder 'I-i’m warning you! Y-you better go away!’." Asriel was sinking down, hoping it wouldn’t get much scarier. He wasn’t really a fan of scary stories. 

"Suddenly, a dark figure appeared in the closet! It’s eyes glowed. 'You should start running’ it said very quietly. So I ran out of the room but it was right behind me!” Frisk started to notice Asriel getting a bit uncomfortable, that was their cue to wrap it up. “ I was running but it got closer and closer, until I tripped. It got closer to me but before I could get up and run away again…” Frisk started leaning forward to build suspense. “It was right there. I screamed 'Who are you?!’ And do you know what it said?” Frisk asked and turned off the flashlight, plunging the two into darkness. Asriel only shook his head in reply as he gripped the bedsheets.

"It leaned forward and said… 'Why, I’m the tickle monster, of course!’“ At this moment Frisk jumped forward and latched on to Asriel’s sides eliciting a squeak and frantic laughter from the boy. 

"Frisk! Nahahahah!” Asriel squealed and laughed as he shot his arms down to his sides and squirmed around under the sheets. Frisk grabbed and yanked the comforter off the two of them so they could see each other. 

“Asriel! Hold still! Or you’ll make the tickle monster angry!” Frisk laughed along with Asriel, relishing in the almost angelic laughter pouring from his mouth.

“Stohohohp! You’re sohohoho mehehehehean!” Asriel shouted at Frisk without any actual spite. Frisk had figured out pretty quickly that Asriel really liked this. He loved the playful atmosphere, the laughter, the contact. And Frisk was happy to give that to him.

“Oh, that’s it! The tickle monster’s angry now!” Frisk quickly shot one hand to scribble against his stomach while the other continued to kneed into his sides. Asriel squealed again at the sudden relocation and laughed harder, all the while gripping the bed sheets to keep himself from batting at Frisk’s hands since he didn’t actually want it to stop. “It’s cute how you don’t even try to get away.”   
Asriel felt a blush form underneath his white fur. They tended to dance around flirting every so often. Asriel assumed it was because Frisk seemed to flirt with just about everyone, but the constant flirtatious comments, compliments and cuddling seemed more persistent and promising than that, or so he hoped. Asriel would have said something if he wasn’t laughing so hard.  
Frisk smiled brightly down at the happy figure beneath them. Asriel always seemed so joyful when they did this. Frisk decided to kick things up a notch, so they took the hand that was kneading into Asriel’s sides and instead went to wiggle against his neck. Asriel’s shoulders shot up instinctively as giggles erupted from his mouth, giving Frisk access to his underarms. Once they reached there it was all over for Asriel. 

“NOHOHOHO! FRIHIHIHSK! NOHOHOT THEHEHEHERE!” Asriel was reduced to loud hysterical laughter as his arms once again slammed down to his sides, only proceeding to trap Frisk’s hands there, and his fists pounded the bed. 

"Why not here? It seems like a great spot.“ Frisk giggled at the adorable scene before them. Asriel on his back, fur messy, eyes squeezed shut and snout split open in a wide happy smile showing his small, cute fangs as he shook his head back and forth frantically. Frisk slowed his fingers to a halt and waited for Asriel to gain his composure back. 

Asriel stilled, panting with an ever-present smile. When his breathing slowed to normal, he opened his eyes and stared back at Frisk. "Th-Thanks, Frisk” Asriel glanced down sheepishly. Frisk chuckled at him, brushing his ear which was bent backwards so that it was in a better position. His fur was so soft and almost like silk. Frisk lowered themselves so they were laying next to Asriel on their side. They put an arm on his side and they both and sat in silence, until Asriel pulled Frisk closer and said “Now I’m too tired to get up.” Frisk only laughed in response. A glance at the clock showed it was past their bedtime. Around 10:30. Asriel rested his head on top of Frisk’s and smiled. “Guess I’ll just stay here with you.”

"Fine with me, Azzy.“ Asriel smiled brighter at the nickname. Frisk snuggled into the warm fur, closing their eyes and listening to Asriel’s heart beat. "Good night.”

"Good night, Frisk.“ Asriel whispered into the darkness, and closed his eyes, happily cuddling his soulmate.


	2. The Big Bad Tickle Monster's Back

**Summary for the Chapter:**

> A sequel to “The Big Bad Tickle Monster”. Asriel wakes up with a craving for revenge. Tickle fight ensues. (originally posted May 9th 2016)

Two beings. One soul. 

All Asriel felt was the warmth of his soulmate against his fur. Sunlight peeked through the window onto the two cuddled up figures on one bed. The human child was laid on top of the young monster, each one hugging the other tightly under the purple comforter. Asriel woke up enough to figure out what was happening and to savor it. All was silent. The only sign of life was the steady rise and fall of breathing. After Frisk tickling Asriel to pieces last night the two fell asleep together. Asriel smiled at the memory. He loved the little tickle wars they shared. But last night was a bit more of a one-sided tickle fight, which was fun too. But tickle fights were way better. 

Asriel eyed the child on top of him, mischief creeping into his smile. He gently moved his hand upward until it rested on Frisk’s side and softly skittered his fingers across. 

“Mmm… Azzy… Stohoppihit…” Frisk giggled with a sleepy smile. Asriel’s eyes lit up at the adorable reaction. 

“Stop what?” Asriel replied teasingly as he wiggled his fingers a bit faster. 

“Youhouhouhou knohohow whahahat.” Frisk finally opened their eyes and stared at the boy beneath them with a wide playful smile. Asriel only smirked back.

“Oh! You mean my revenge for last night?” Asriel slowly moved his other hand to Frisk’s other side and rubbed his hand across letting his silky soft fur do all the work. Frisk erupted in giggles they tried to hide. 

“Whahahat doho youhouhou mehehean revehehenge?” Frisk squealed as Asriel’s fur reached up at their ribs. “I thouhouhought youhouhou lihihiked ihihit!”

“I never said I didn’t.” Asriel added trying to suppress his own laughter at the adorable high-pitched giggles. He quickly moved over on his side, moving Frisk as he did so until both of them were laying on their side facing each other.

“Thehehen whaha-?” Frisk tried to ask but was cut off when Asriel moved his hand down to scribble across their belly. “NAHAHA AHAHAZZY!” 

“Yes Frisk?” Asriel asked. At that moment Asriel felt hands clutch at his sides and fingers dig into his soft fur. He immediately let go of Frisk and curled in to protect his sides all while squealing and laughing.

“I was trying to say then why do you need revenge, but I think I figured out why. You just wanna have a tickle fight!” Frisk emphasized ‘tickle fight’ by shooting his hands under Asriel’s arms and watching him practically scream with laughter.  
In desperation, Asriel jolted to the side carrying both him and Frisk tumbling onto the floor along with the quilt and some pillows. Asriel was hidden under the fallen comforter panting and still giggling. Frisk, however, was working on throwing off the comforter to attack his victim once more. Once the quilt was off Asriel stared up in fear and excited anticipation of what was to come. Frisk teasingly held up their hands and wiggled their fingers making Asriel giggle harder. 

“I’m gonna get ya Azzy!” Asriel bounded up laughing and running out of the room 

“YOU’LL HAVE TO CATCH ME FIRST!” Asriel called back still laughing playfully.

“YOU’RE SO GONNA GET IT NOW AZZY!” With that, Frisk took off out of the room after their soulmate.

Asriel was running down the stairs with Frisk close behind. He grabbed the end of the railing to make a sharp turn into the living room and Frisk did the same. As they entered the living room Frisk jumped and tackled Asriel down, grabbing his sides and scribbling with all ten fingers. Asriel fell down in a heap of laughter with Frisk following and straddling him on the carpet.

“THE TICKLE MONSTER’S BACK FOR REVENGE!” Frisk shouted with an evil grin on their face. Asriel only laughed and pounded the ground with his fists at the maddening ticklish sensations jumping from his sides to his underarms and everywhere in between.

“Um… Whatcha kiddos doing?” 

Frisk and Asriel both paused to realize that Sans had walked in.

“Just playing a game.” Frisk responded while starting to climb off Asriel who was blushing from embarrassment.

“Well alrighty. But Undyne and Alphys are still sleepin’ and you’re so loud you’re rattling my bones.” Sans added with his signature grin.

Frisk and Asriel both laughed at the pun before Frisk had a sudden idea.

“Okay, but how about you play a game with us?”

“Uh… sure. Whaddya wanna play?” Sans asked. Asriel was slowly catching on.

“It’s called tickle monster!” And with that the soulmates launched at the skeleton starting yet another tickle war.

[To be continued?]


	3. The Big Bad Tickle War

**Summary for the Chapter:**

> Part 3 of Big Bad Tickle Monster. Frisk and Asriel try to tickle Sans. Emphasis on ‘try’. Sans goes to get back at them and it ends up in a chase which leads to a huge tickle war between Frisk, Asriel, Sans, Papyrus, and Undyne. (originally posted May 12th 2016)

“It’s called ‘Tickle Monster’” 

Asriel and Frisk simultaneously launched at the skeleton who was rearing back in surprise. Frisk made first impact as he dove into Sans’ ribs sending them tumbling to the ground. Asriel followed close behind, jumping at the feet and pinning them down to keep them from squirming. 

“Don’t you kids dare-NOHOHO-!” Sans was cut off by his sudden shriek of laughter as Frisk shoved their hands under his jacket and latched on to the sensitive ribs. Asriel was working on getting a slipper off with one hand as the other hand was lightly scratching under Sans’ knee. The force of the skeleton’s kicking was almost enough to knock Asriel off the legs entirely, but he somehow managed to keep on. He pulled of the slipper and rubbed against the bones of the arch causing a peak in laughter emanating from the skeleton. His laughter was loud, low-pitched, and boisterous, Asriel was relishing in the sound before the mass underneath him suddenly disappeared. Asriel was on the ground, taken aback, along with an equally confused Frisk. He looked around him until he spotted the flustered skeleton across the room catching his breath. Sans’ eye was a brilliant blue with a wisp of magic radiating from it. Asriel felt his blood run cold as the skeleton turned to stare at them with a grin wider than usual.

“I warned ya. I told ya to stop. Now I’m gonna ask… Do ya wanna have a bad time?”

Asriel shot a terrified look at Frisk who glanced back with a nervous smile in response. 

“Run.” That was all Sans needed to say before the two kids took off running giggling nervously and excitedly.

“What do we do?!” Asriel shouted at Frisk as the two ran up the stairs.

“We hide for now, we’ll get him after he stops chasing us! Now go!” Asriel shot to the left and Frisk went the opposite direction. Asriel was having the time of his life. It felt so scary yet fun at the same time when you had an ultra-powerful magic skeleton chasing after you with the intent to tickle the crap out of you. And they seemed like they were having some kind of tickle war with the way Frisk was talking. Asriel couldn’t have asked for a better morning. 

He was snapped out of his thoughts when he heard Sans’ voice echoing through the halls.

“Come out wherever you are, I have a bone to pick with you…” Asriel cringed at the pun but couldn’t focus on it for too long as he had to figure out where to hide. The hall he ran down had a bathroom connected to Undyne and Alphys’ room. Not a lot of options. He ran to the bathroom and knocked hurriedly to make sure no one was in there, when there was no answer he through open the door and dashed inside, closing the door behind him and flicking off the lights. Though he liked being tickled, Sans had some kind of freaky magic powers he would probably use, which was scary to think about. Plus, the chase made it more fun. He crouched underneath the sink, heart pounding from the running and the suspense. He waited for a bit until he saw the door knob to the hall turn. His heart sank. He was about to make a break for it when, instead of a vengeful skeleton, Undyne walked in the room.

“Hey, I heard something in here. Who’s there?”

“Me. Uh… Howdy.” Asriel said timidly.

“Oh, hey Asriel… Why are you hiding under the sink?” Undyne looked down with a confused but amused expression.

“Oh! Uh… Sans is chasing me and Frisk…”

“Oh!” Undyne let out a chuckle. “What’d you do?”

“Um… We… uh, tickled him?” Asriel mumbled shyly. Undyne broke out in laughter.

“The little skeletons TICKLISH!? That’s good to know for later! So, lemme guess… he’s threatening to tickle you back?” Undyne stood tall, looking down at the crouching boy, amused.

“Uh… Yeah. Please don’t tell him where I am!” Asriel looked up pleadingly, slowly coming out from the uncomfortable position. He had a bad feeling about the way Undyne was looking at him.

“Oh yeah! I won’t tell Sans… It’s me you gotta worry about!” Asriel immediately darted out from under the sink laughing excitedly. He tried to get past the taller monster but she was too fast, quickly grabbing him by the chest and moving her hands to his sides. 

Asriel shrieked with high-pitched laughter at the sudden sensation. His eyes squeezed shut and his arms clamped down to his sides.

“NAahaha! Undyyhyhyh-” he was reduced to laughter easily, but was still in an upright position which gave him some hope for escape. He squirmed away, grabbing the door frame for leverage before struggling enough to barely escape the tight grasp. He dashed out of the bathroom followed by Undyne close behind. This really was a tickle war.

“You can’t run from me! Fwuhahahaha!” Asriel was running down the stairs as fast as his feet could carry him with a wide, excited smile on his face. He grabbed on to the banister to make a sharp left turn into other hall. He blindly ran into the first room and slammed the door behind him. When he calmed down enough to fully figure out his surroundings, he realized he had accidentally entered Papyrus’ room. On the racecar bed was a confused and slightly alarmed skeleton staring at the new visitor.

“ASRIEL? WHAT HAS YOU SO SCARED? AND RUNNING INTO MY ROOM?” Asriel looked at him. He didn’t want to add another into the tickle war. Or did he? It wouldn’t be that bad. It could be pretty fun actually! 

“Undyne is chasing me and trying to tickle me. Me, Frisk, Undyne and Sans are all having a tickle war.”

“A TICKLE WAR? HOW FUN! MAY THE GREAT PAPYRUS JOIN?” Papyrus looked eagerly at Asriel.

“Sure! You can be on me and Frisk’s side! We’re against Sans and Undyne. The goal is basically to tickle people on the other side.” Asriel was smiling in amusement at Papyrus’ hopeful and eager look.

“A WISE CHOICE TO HAVE ME ON YOUR SIDE! FEAR NOT, CHILD! I, THE GREAT PAPYRUS, WILL WIN THIS TICKLE WAR!” Papyrus stood and proudly announced.

“Good, now-” Asriel was interrupted by a pounding on the door. 

“OPEN UP ASRIEL! I KNOW YOU’RE IN THERE! Came Undyne’s intimidating voice from the other side.

Papyrus walked to the door and spoke through it. “UNDYNE! THE CHILD HAS RECRUITED ME ONTO THEIR SIDE. THEREFORE I AM AGAINST YOU. I WILL HAVE YOU KNOW I INTEND TO WIN THIS WAR!” Asriel could hear Undyne’s heavily amused laughter from the other side.

“Oh yeah? Why don’t you open the door then?”

“VERY WELL!” Asriel stared as Papyrus opened the door revealing Undyne standing in a fierce pose. She looked at Papyrus and then launched. Tackling him to the ground, she latched her fingers onto Papyrus’ vulnerable spine and he almost instantly fell into hysterics.

“Don’t forget, dork, I know your weaknesses! Fwuahaha!”

“NAHAHA UNDYHYHYNE” Asriel wondered if she’d ever done that before, seeing as she immediately zeroed in on his seemingly worst spot. Asriel was snapped out of his thoughts when Undyne looked up and locked eyes with him, a mischievous grin sneaking onto her face. He suddenly dashed out of the room again, he was getting tired of all the running but as soon as he exited the room he slammed into a familiar figure. He looked up and was face-to-face with Sans. Glowing blue magic eye and all. The large grin 

Sans wore only served to intimidate Asriel more. The skeleton moved a hand out of his hoodie pockets and started moving it upwards. Suddenly his chest shook as Sans moved his hand high, Asriel floated up with it. He turned his soul blue. 

“Not getting away this time, kiddo.” Suddenly they were in the living room. Damn his magic powers. Those were so unfair. 

“You’re about to have a bad time.” That was all Asriel heard before his soul returned to normal, he dropped to the ground. He felt a rush of adrenaline. He was terrified and excited at the same time. The skeleton teleported directly behind him and dug into his   
ribs with all ten fingers. Asriel screamed with laughter. His arms shot to his sides and his eyes squeezed shut. As the fingers wandered all over his sensitive skin loud laughter flew past his lips as he squirmed and thrashed wildly.

“Jeez kiddo, you’re really frickin’ ticklish.” Finally Sans gave up that intimidating act, it was starting to become kinda scary, not that Asriel could relish in Sans’ normal, comforting voice when he was in pieces with laughter. Sans had started to move one hand to his underarms and the other to his stomach. Asriel was squealing, snorting, laughing, screaming, and everything in between. He loved the overwhelming sensations but would prefer it if Frisk did it, he wasn’t as acquainted with Sans as Frisk was. But he still loved the playful and engaging torture that left him screaming for mercy but hoping for more. Just as his eyes were starting to tear up he heard a loud but familiar voice.

“I’M COMING AZZY!” Suddenly he heard Sans yell something, the sensations stopped and Asriel could breathe again. He looked behind him and saw Sans struggling to get a bedsheet off his face with Frisk panting beside him. 

“Really?” Pant. “A Bedsheet-” Pant. “…was all you-” Pant. “…could come up with?” Pant.

Frisk looked at Asriel with an annoyed expression. “You try coming up with a way to incapacitate a magic skeleton! and I just saved you, you should- Oh no! He’s getting up!” Asriel refrained from saying ‘Kinda expected that.“ and instead feared for his sanity with the skeleton smiling above them, again with the signature wisp of magic. Without thinking, Asriel dove at him to take him down before he could attack. He remembered Undyne’s earlier move on Papyrus and dug under Sans’ jacket until Asriel’s hand reached his spine. 

He did not expect what happened next.

Instead of teleporting away, Sans screamed with laughter and kicked and flailed franticly. Both he and Frisk were shocked at the new discovery. 

"NAHAHA STAHAHAP!” Sans squeezed his eyes shut yet the brilliant blue magic wisp only glowed through and shot around wildly. It seemed Sans couldn’t teleport away due to the maddening and distracting tickling on his most sensitive spot. His screams of laughter had attracted Undyne and Papyrus. Both stood near Frisk and stared at the scene, laughing. Asriel was sitting on top of Sans with one hand under his jacket and Sans was hysterical, emitting an incredible magic glow.

“MERHERHERHERHERCY! PLEAHEAHEAHEAHEASE!” Then his laughter went silent and Asriel hopped off.

“I’m sorry… Did I take it too far?” Asriel asked timidly.

“Nah, don’t worry about, punk! He’ll be fine.” Undyne answered him and gave him a friendly punch in the arm. Asriel rubbed at the spot because it seems like she doesn’t know her own strength and stared at Sans on the ground. He was panting with a wide, happy smile and eyes still shut. The magic blue glow had died down but was still present, whipping from side to side as Sans recovered. 

“I DECLARE THIS A WIN FOR TEAM PAPYRUS!” Frisk and Asriel laughed at that and Undyne just rolled her eyes. 

“Well-” Pant. “…you tickled-” Pant. “…my funny bone-” Pant. “…kid.” Sans opened his one magic eye to look at the now screaming mad Papyrus and two chuckling children.

“OH MY GOD, SANS! YOU RUINED THIS VICTORY!” After watching Papyrus flip out and Sans laugh at his brother’s antics, Frisk walked to Asriel, trapped him in a hug from behind and whispered into his soft, fluffy ear. “Just because I saved you from Sans, don’t think this is over. I just saved all the fun for myself.” Frisk smirked as Asriel’s face grew warm, a blush burning beneath his fur. “Hey, I took down Sans! Don’t think I won’t do it to you too!” Asriel added with false confidence. “I guess this tickle war is just on hold for now, then.” Frisk added, smiling into the fur on Asriel’s neck, humming to give subtle tickles and keep Asriel giggling. It most certainly wasn’t over.


End file.
